<!-- HTML header for doxygen 1.8.8-->
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <!-- For Mobile Devices -->
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/>
        <meta name="generator" content="Doxygen 1.8.20"/>
        <script type="text/javascript" src="https://code.jquery.com/jquery-2.1.1.min.js"></script>
        <title>libevdev: Compatibility and Behavior across kernel versions</title>
        <!--<link href="tabs.css" rel="stylesheet" type="text/css"/>-->
        <script type="text/javascript" src="dynsections.js"></script>
        <link href="search/search.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="search/searchdata.js"></script>
<script type="text/javascript" src="search/search.js"></script>
        <link href="doxygen.css" rel="stylesheet" type="text/css" />
        <link href="bootstrap.css" rel="stylesheet" type="text/css"/>
<link href="customdoxygen.css" rel="stylesheet" type="text/css"/>
<link href="libevdevdoxygen.css" rel="stylesheet" type="text/css"/>
        <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js"></script>
        <script type="text/javascript" src="doxy-boot.js"></script>
    </head>
    <body>
        <nav class="navbar navbar-default" role="navigation">
            <div class="container">
                <div class="navbar-header">
                    <a class="navbar-brand">libevdev 1.10.0</a>
                </div>
            </div>
        </nav>
        <div id="top"><!-- do not remove this div, it is closed by doxygen! -->
            <div class="content" id="content">
                <div class="container">
                    <div class="row">
                        <div class="col-sm-12 panel panel-default" style="padding-bottom: 15px;">
                            <div style="margin-bottom: 15px;">
<!-- end header part -->
<!-- Generated by Doxygen 1.8.20 -->
<script type="text/javascript">
/* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&amp;dn=gpl-2.0.txt GPL-v2 */
var searchBox = new SearchBox("searchBox", "search",false,'Search');
/* @license-end */
</script>
<script type="text/javascript" src="menudata.js"></script>
<script type="text/javascript" src="menu.js"></script>
<script type="text/javascript">
/* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&amp;dn=gpl-2.0.txt GPL-v2 */
$(function() {
  initMenu('',true,false,'search.php','Search');
  $(document).ready(function() { init_search(); });
});
/* @license-end */</script>
<div id="main-nav"></div>
<!-- window showing the filter options -->
<div id="MSearchSelectWindow"
     onmouseover="return searchBox.OnSearchSelectShow()"
     onmouseout="return searchBox.OnSearchSelectHide()"
     onkeydown="return searchBox.OnSearchSelectKey(event)">
</div>

<!-- iframe showing the search results (closed by default) -->
<div id="MSearchResultsWindow">
<iframe src="javascript:void(0)" frameborder="0" 
        name="MSearchResults" id="MSearchResults">
</iframe>
</div>

</div><!-- top -->
<div class="PageDoc"><div class="header">
  <div class="headertitle">
<div class="title">Compatibility and Behavior across kernel versions </div>  </div>
</div><!--header-->
<div class="contents">
<div class="textblock"><p>This page describes libevdev's behavior when the build-time kernel and the run-time kernel differ in their feature set.</p>
<p>With the exception of event names, libevdev defines features that may be missing on older kernels and building on such kernels will not disable features. Running libevdev on a kernel that is missing some feature will change libevdev's behavior. In most cases, the new behavior should be obvious, but it is spelled out below in detail.</p>
<h1><a class="anchor" id="autotoc_md14"></a>
Minimum requirements</h1>
<p>libevdev requires a 2.6.36 kernel as minimum. Specifically, it requires kernel-support for <code>ABS_MT_SLOT</code>.</p>
<h1><a class="anchor" id="autotoc_md15"></a>
Event and input property names</h1>
<p>Event names and input property names are defined at build-time by the linux/input.h shipped with libevdev. The list of event names is compiled at build-time, any events not defined at build time will not resolve. Specifically, <a class="el" href="group__misc.html#gab407b3c2caaae502859c28460cad17bb">libevdev_event_code_get_name()</a> for an undefined type or code will always return <code>NULL</code>. Likewise, <a class="el" href="group__misc.html#gacc12bdb7b912070ac9c375428f2c9892">libevdev_property_get_name()</a> will return NULL for properties undefined at build-time.</p>
<h1><a class="anchor" id="autotoc_md16"></a>
Input properties</h1>
<p>If the kernel does not support input properties, specifically the <code>EVIOCGPROPS</code> ioctl, libevdev does not expose input properties to the caller. Specifically, <a class="el" href="group__bits.html#ga36d529ea53f4522004bc7d16c051464b">libevdev_has_property()</a> will always return 0 unless the property has been manually set with <a class="el" href="group__kernel.html#gafc552080520c9d886452b05f3a1d75b6">libevdev_enable_property()</a>.</p>
<p>This also applies to the libevdev-uinput code. If uinput does not honor <code>UI_SET_PROPBIT</code>, libevdev will continue without setting the properties on the device.</p>
<h1><a class="anchor" id="autotoc_md17"></a>
MT slot behavior</h1>
<p>If the kernel does not support the <code>EVIOCGMTSLOTS</code> ioctl, libevdev assumes all values in all slots are 0 and continues without an error.</p>
<h1><a class="anchor" id="autotoc_md18"></a>
SYN_DROPPED behavior</h1>
<p>A kernel without <code>SYN_DROPPED</code> won't send such an event. <a class="el" href="group__events.html#gabb96c864e836c0b98788f4ab771c3a76" title="Get the next event from the device.">libevdev_next_event()</a> will never require the switch to sync mode. </p>
</div></div><!-- contents -->
</div><!-- PageDoc -->
<!-- HTML footer for doxygen 1.8.8-->
<!-- start footer part -->
</div>
</div>
</div>
</div>
</div>
<hr class="footer"/><address class="footer"><small>
Generated by &#160;<a href="http://www.doxygen.org/index.html">
<img class="footer" src="doxygen.png" alt="doxygen"/>
</a> 1.8.20
</small></address>
</body>
</html>
